Patch: Dwarf2 reader -vs- DW_OP_piece

Tom Tromey
2002-02-21T18:53:05Z

I just submitted a change that changes gcc's Dwarf-2 output.
It hasn't been approved yet, but of course I'm hoping it will be.
With this change gcc will now generate DW_OP_piece when a value spans
multiple registers.

I came up with a somewhat hacky gdb patch to ignore DW_OP_piece.

I'm hoping this patch is just a stopgap until someone adds real
Dwarf-2 location expression support to gdb.

Ok?

Tom

Index: ChangeLog
from Tom Tromey <tromey@redhat.com>

* dwarf2read.c (decode_locdesc): Recognize DW_OP_piece.

Index: dwarf2read.c
===================================================================
RCS file: /cvs/src/src/gdb/dwarf2read.c,v
retrieving revision 1.48
diff -u -r1.48 dwarf2read.c
--- dwarf2read.c 2002/02/15 22:42:33 1.48
+++ dwarf2read.c 2002/02/21 18:49:43
@@ -5808,6 +5808,7 @@
int stacki;
unsigned int bytes_read, unsnd;
unsigned char op;
+ int last_was_piece = 0;

i = 0;
stacki = 0;
@@ -5891,8 +5892,13 @@
case DW_OP_reg29:
case DW_OP_reg30:
case DW_OP_reg31:
- isreg = 1;
- stack[++stacki] = op - DW_OP_reg0;
+ if (last_was_piece)
+ last_was_piece = 0;
+ else
+ {
+ isreg = 1;
+ stack[++stacki] = op - DW_OP_reg0;
+ }
break;

case DW_OP_regx:
@@ -6043,6 +6049,14 @@
this using GDB's address_class enum. */
if (i < size)
complain (&dwarf2_complex_location_expr);
+ break;
+
+ case DW_OP_piece:
+ /* For now we essentially ignore this. We assume it only
+ occurs when a value spans multiple registers. */
+ read_unsigned_leb128 (NULL, (data + i), &bytes_read);
+ i += bytes_read;
+ last_was_piece = 1;
break;